The present application claims priority under 35 U.S.C. xc2xa7119 to Japanese Patent Application Nos. 2001-284898 and 2001-284899 filed on Sep. 19, 2001, the entire contents of which are hereby incorporated by reference.
1. Field of the Invention
The present invention relates to a lubrication unit for a vehicle internal combustion engine, and more specifically to a dry-sump lubrication unit for a so-called vertical internal combustion engine having a crankshaft disposed in parallel with the traveling direction of the vehicle body.
2. Description of Background Art
One example of a dry-sump lubrication unit for a vertical internal combustion engine is disclosed in JP-A-2001-73736, in which a transmission chamber is disposed outside the crankshaft. A main shaft and a countershaft are disposed one above the other and constituting the transmission, with an output shaft disposed below the countershaft. An oil tank is disposed further outside the transmission chamber so that the lower end thereof extends to a position below the output shaft.
One problem associated with the lubrication unit of JP-A-2001-73736 is that the oil tank is disposed at the position significantly leaned on one side in the widthwise direction of the vehicle body, whereby the entire width of the engine increases and thus the loadability on the vehicle is deteriorated when the engine displacement is large and thus the transmission gear is upsized.
In order to solve the aforementioned problems in the related art, a first aspect of the present invention provides a dry-sump lubrication unit for an internal combustion engine disposed so that a crankshaft is disposed in parallel with the direction of travel of the vehicle body, comprising an oil tank disposed in a crankcase located at the substantially lower center when viewed from the front or back of the vehicle body on the rear side with respect to the traveling direction and/or in a space between the crankcase and the rear case cover.
Since the present invention is constructed in such a manner that, as described above, the oil tank is disposed at the substantially lower center when viewed from the front or back of the vehicle body, variations in liquid surface of oil due to shaking of the vehicle body can be minimized.
Furthermore, since the oil tank is disposed in the crankcase positioned on the rear side with respect to the traveling direction and/or in a space between the crankcase and the rear case cover, the space can be utilized effectively.
According to a second aspect of the present invention the oil pump is disposed forwardly of the oil tank. Therefore, the space can further be utilized effectively, and thus the entire power unit can be downsized.
According to a third aspect of the present invention, a crankshaft is disposed so as to lean widthwise on one side when viewed from the front or back of the vehicle body, a transmission shaft disposed on the other side thereof, an oil tank is disposed at the substantially widthwise center on the rear side of the vehicle body, and an oil injection pipe extends from the oil tank toward the side surface thereof on the transmission side.
Since the present invention is constructed in such a manner that, as described above, the crankshaft is disposed so as to be leaned widthwise on one side when viewed from the front or back of the vehicle body, the transmission is disposed on the other side thereof, and the oil tank is disposed at the substantially widthwise center on the rear side of the vehicle body, the space is effectively used, and thus the entire power unit can be downsized. In addition, since the oil tank is disposed at the substantially widthwise center of the vehicle body, variations in liquid level of oil due to shaking of the vehicle body is restrained, and a suction port of the oil pump is prevented from being affected by inclination, thereby stabilizing the lubrication pressure.
Since the oil injection pipe is provided so as to extend from the oil tank to the side surface thereof on the side of the transmission, replenishment or replacement of oil may be performed easily. In addition, since the position of the oil tank is not restricted in terms of workability, the space in the crankcase can be used effectively, and the crankcase may be downsized. Further, the oil tank can be placed at the center of the power unit as described above.
Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.